A color Doppler mode image expresses fluid object information of a fluid object such as a blood flow, e.g., velocity, power, and variance components, in color, by using the color Doppler method. At the time of ultrasonic examination, a color Doppler mode image is superimposed and displayed on a B-mode image.
Antenatal ultrasonic examination is performed by using these techniques. As an example of an application of the internal ultrasonic examination method, there is available a technique of displaying a three-dimensional image of a fetus in the womb.
In performing antenatal ultrasonic examination, a doctor detects an intraplacental blood flow, diagnoses fetal development or a placental state, or checks the presence/absence of a disease such as an arteriovenous shunt. At the time of antenatal ultrasonic examination, the amniotic fluid moves due to the movement of a fetus or the like. In this case, the fluid object information of the moving amniotic fluid overlaps a placental cortex portion or the like on an image. It is therefore difficult to observe a blood vessel in the placental cortex portion. In addition, when the fetus is close to the placenta, it is very difficult to observe the placenta.